Electric operating machine

ABSTRACT

When a main switch ( 12 ) is turned ON, an electric operating machine ( 1 ) is put in the standby mode. With a trigger ( 13 ) being pulled in the standby mode, a power supply circuit ( 16 ) applies a voltage to a drive part ( 30 ). The power supply circuit ( 16 ) adjusts the voltage applied to the drive part ( 30 ) for a voltage corresponding to the pulling rate of the trigger ( 13 ). When the current running toward the drive part ( 30 ) exceeds the rated value of the drive part ( 30 ), the power supply circuit ( 16 ) automatically stops power supply to the drive part ( 30 ). On the other hand, when the output voltage of a battery ( 50 ) drops and the battery ( 50 ) is put in an overdischarge state, power supply to the drive part ( 30 ) is automatically stopped. When it is detected that the battery ( 50 ) undergoes an abnormal event, power supply to the drive part ( 30 ) is automatically stopped.

TECHNICAL FIELD

The present invention relates to an electric operating machine driven bya motor.

BACKGROUND ART

Recently, electric operating machines having a motor that drives arotary blade (for example, electric lawn mowers) attract attention andare increasingly used. Using electric power as power source, electricoperating machines (lawn mowers) are quiet, discharge no exhaust gas,and excellent in running cost.

For example, Patent Literature 1 discloses an electric lawn mower havingadjustable motor rotation speed. This electric lawn mower has aconverter to change the voltage applied to the motor so as to change themotor rotation speed. Then, the blade rotation speed can be changedaccording to the lawn grass to mow or the lawn shape. Electric drivingproduces low driving noise.

CITATION LIST Patent Literature

-   [PTL 1]-   Unexamined Japanese Patent Application KOKAI Publication No.    2006-217843.

SUMMARY OF INVENTION Technical Field

The electric lawn mower described in the Patent Literature 1 changes therotation speed according to the battery output. Therefore, when abattery of different output is mounted, the motor does not rotate at adesired rotation speed, which is inconvenient. Furthermore, batterieshave different weights depending on their output. When a battery ofdifferent output is mounted, the weight balance of the electric lawnmower is changed, which may lower the operability.

The present invention is made in view of the above problems and apurpose of the present invention is to provide an electric operatingmachine that can control the rotation speed of the motor regardless ofthe output of the battery mounted and allow for mounting/dismounting ofbatteries of different outputs. Furthermore, another purpose of thepresent invention is to provide an electric operating machine that islightweight and well-balanced and therefore excellent in operability.

Solution to Problem

In order to achieve the above purpose, the electric operating machineaccording to the first aspect of the present invention is:

an electric operating machine comprising:

a power source part including a battery mounting part for mounting abattery;

and a voltage conversion part converting and outputting the voltageinput from the battery; and

an electric motor to which a work tool rotating in association therewithis connected and that rotates upon application of the voltage outputfrom the voltage conversion part, characterized in that

the power source part further includes a voltage measuring partmeasuring the voltage applied to the electric motor and outputting it tothe voltage conversion part is further provided; and

the voltage conversion part adjusts the output voltage so that thevoltage output from the voltage measuring part has a given level.

For example, a battery of any voltage is mounted on or dismounted fromthe battery mounting part.

The power source part of the electric operating machine may furthercomprise an overcurrent protection part blocking the current runningtoward the electric motor when the current running toward the electricmotor exceeds a given value.

Furthermore, the electric operating machine may further comprise a firstannouncing part announcing that an overcurrent is running when thecurrent running toward the electric motor exceeds a given value.

The power source part of the electric operating machine may furthercomprise an overdischarge protection part blocking the current runningtoward the electric motor when the voltage output from the batterybecomes lower than a predetermined voltage.

Furthermore, the electric operating machine may further comprise asecond announcing part announcing that the battery is overly dischargingwhen the voltage output from the battery becomes lower than apredetermined voltage.

Furthermore, the power source part of the electric operating machine mayfurther comprise a voltage determination part determining thepredetermined voltage based on battery information of the battery thatis output from the battery.

Furthermore, the power source part of the electric operating machine mayfurther comprise a battery abnormality stop part blocking the currentrunning toward the electric motor according to battery abnormalitysignals output from the battery when the battery undergoes an abnormalevent.

Furthermore, the battery abnormality stop part may block the currentrunning toward the electric motor until the battery is dismounted fromthe battery mounting part since it receives the battery abnormalitysignals.

Furthermore, the electric operating machine may further comprise a thirdannouncing part announcing that the battery undergoes an abnormal eventwhen the battery undergoes an abnormal event.

Furthermore, it is possible that:

the electric operating machine further comprises a trigger, and

the voltage measuring part applies to the voltage conversion part avoltage according to the pulling rate of the trigger.

Furthermore, the power source part of the electric operating machine mayfurther comprise a trigger switch part blocking the current runningtoward the electric motor when the pulling rate of the trigger is lowerthan a given rate and allowing a current to run through the electricmotor when the pulling rate of the trigger is equal to or higher thanthe given rate.

The power source part of the electric operating machine may furthercomprise a main switch part blocking the current running from thebattery to the trigger switch part when it is turned OFF and allowingthe current when it is turned ON.

Furthermore, for example, the electric operating machine may furthercomprise a first light emitting part emitting light when the main switchpart is ON.

Furthermore, the electric operating machine may further comprise aremaining battery level display displaying the remaining battery levelaccording the voltage output from the battery.

Furthermore, the power source part of the electric operating machine maycomprise a constant voltage circuit outputting a constant voltage fromthe voltage output from the battery.

Furthermore, the electric operating machine may further comprise a soundreproducing part operating upon application of a voltage output from theconstant voltage circuit, decoding sound data, and reproducing soundinformation.

Furthermore, the electric operating machine may further comprise a radiooperating upon application of a voltage output from the constant voltagecircuit and detecting sound information in radio waves received by anantenna.

Furthermore, the electric operating machine may comprise a speakeramplifying the sound information and making sound by a voltage outputfrom the constant voltage circuit.

Furthermore, it is preferable that the electric motor is a corelessmotor.

Furthermore, the electric operating machine may further comprise acoupling part on whose one end the power source part is arranged and onwhose other end the electric motor is arranged.

Furthermore, the electric operating machine may comprise a second lightemitting part emitting light when the electric motor is powered.

Furthermore, the electric operating machine may further comprise afourth announcing part announcing the power supply when the electricmotor is powered.

Furthermore, it is possible that:

the coreless motor includes a rotor and a stator;

the rotor includes a fixed output shaft;

one of the rotor and stator comprises a disc-shaped coil substrateincluding multiple nearly annular coils arranged in the circumferentialdirection around the output shaft when seen in the axial direction ofthe output shaft; and

the other of the rotor and stator comprises a magnet generating amagnetic flux passing through the coil substrate in the axial directionof the output shaft.

Furthermore, in order to achieve the above purpose, the electricoperating machine according to the second aspect of the presentinvention is:

an electric operating machine comprising:

a coreless motor;

a power source part comprising a mounting part to which a lithiumrechargeable battery is detachably mounted; and

a coupling part holding the coreless motor at one end and holding thepower source part at the other end, characterized in that:

the coreless motor includes a rotor and a stator;

the rotor includes a fixed output shaft;

one of the rotor and stator comprises a disc-shaped coil substrateincluding multiple nearly annular coils arranged in the circumferentialdirection around the output shaft when seen in the axial direction ofthe output shaft; and

the other of the rotor and stator comprises a magnet generating amagnetic flux passing through the coil substrate in the axial directionof the output shaft.

Furthermore, in order to achieve the above purpose, the electricoperating machine according to the third aspect of the present inventionis:

an electric operating machine comprising:

a coreless motor;

a power source part comprising a mounting part to which a rechargeablebattery is detachably mounted;

a coupling part holding the coreless motor at one end and holding thepower source part at the other end;

a grip part extending in the longitudinal direction of the couplingpart, including a trigger operable by the operator for controlling thedrive of the coreless motor, and being continued from or close to thepower source part; and

a handle provided on the coupling part at a distance from the powersource part and grip part for being held by the operator, characterizedin that:

the coreless motor includes a rotor and a stator;

the rotor includes a fixed output shaft;

one of the rotor and stator comprises a disc-shaped coil substrateincluding multiple nearly annular coils arranged in the circumferentialdirection around the output shaft when seen in the axial direction ofthe output shaft;

the other of the rotor and stator comprises a magnet generating amagnetic flux passing through the coil substrate in the axial directionof the output shaft; and

the coreless motor is heavier than the rechargeable battery mounted onthe mounting part and the gravity center of the electric operatingmachine is located on the coreless motor side with respect to thehandle.

Furthermore, the coreless motor may comprise an aluminum alloy motorcase housing the rotor.

Advantageous Effects of Invention

The electric operating machine according to the first aspect of thepresent invention can control the rotation speed of the motor regardlessof the battery output and allow for mounting/dismounting of batteries ofdifferent outputs. Furthermore, the electric operating machinesaccording to the second and third aspects of the present invention arelightweight and well-balanced and therefore excellent in operability.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] An illustration showing the appearance of an electric operatingmachine according to an embodiment of the present invention;

[FIG. 2] An enlarged view of the operation part of the electricoperating machine in FIG. 1;

[FIG. 3] A cross-sectional view of the drive part of the electricoperating machine in FIG. 1;

[FIG. 4] An exploded cross-sectional view of the rotor of the electricoperating machine in FIG. 1;

[FIG. 5] A top view of the rotor in FIG. 4;

[FIG. 6] A top view of the coil substrate part of the rotor in FIG. 4;

[FIG. 7] An illustration showing the connection in the operation part ofthe electric operating machine in FIG. 1;

[FIG. 8] An illustration showing a modification example of the electricoperating machine in FIG. 1;

[FIG. 9]

An illustration showing the connection in the operation part of theelectric operating machine in FIG. 8;

[FIG. 10] A block diagram of the power supply circuit installed in theoperation part of the electric operating machine in FIG. 1;

[FIG. 11] A circuit diagram of a specific example of the booster circuitand speed adjustment part of the power supply circuit in FIG. 10;

[FIG. 12] A circuit diagram of a specific example of the currentdetection part of the power supply circuit in FIG. 10;

[FIG. 13] A circuit diagram of a specific example of the battery voltagedetection part of the power supply circuit in FIG. 10;

[FIG. 14] An illustration showing a modification example of the electricoperating machine in FIG. 1;

[FIG. 15] An illustration showing the electric operating machine in FIG.14 being held;

[FIG. 16] An illustration showing a belt for holding the electricoperating machine in FIG. 14; and

[FIG. 17] An illustration showing the working manner with the electricoperating machine in FIG. 14.

DESCRIPTION OF EMBODIMENTS

The electric operating machine according to an embodiment of the presentinvention will be described hereafter with reference to the drawings.Here, the electric operating machine according to this embodiment is anelectric lawn mower 1 including a motor that drives a rotary blade.

As shown in FIG. 1, an electric lawn mower 1 includes an operation part10, a coupling part 20 held at the forefront of the operation part(power source part) 10 at one end, a drive part 30 held at the other endof the coupling part 20, and a blade (work tool) 39 coupled to the drivepart 30. A battery mounting part 11 is provided at the rear end of theoperation part 10. A main switch 12, a remaining battery level display14, and a main LED (light emitting diode) 15 are provided on the topsurface of the operation part 10. A power supply circuit 16 is providedinside the operation part 10. A D-shaped handle 21 is provided on thecoupling part 20 at a distance from the operation part 10 and a grip 22with a trigger 13 is provided next to the D-shaped handle 21. A runningindicator LED 40 is provided on the top surface of the drive part 30.

The battery mounting part 11 is used to mount a battery 50. The batterymounting part 11 supplies the output of the battery 50 to the powersupply circuit 16.

The main switch 12 is a switch turning ON/OFF the power supply circuit16. When the main switch 12 is turned ON, the power supply circuit 16 isput in the standby mode. The power supply circuit 16 is not activatedand supplies no electric power while the main switch 12 is OFF.

The trigger 13 is a switch controlling the value of electric powersupplied to the drive part 30 from the power supply circuit 16. When thetrigger 13 is pulled in the standby mode while the main switch 12 is ON,the electric power according to the pulling rate of the trigger 13 issupplied to the drive part 30 from the power supply circuit 16.

The remaining battery level display 14 is, for example, a liquid crystalscreen that changes display according to the output of the battery 50.Checking on the screen displayed by the remaining battery level display14, the user of the electric lawn mower 1 can know the approximateremaining operation time.

The main LED 15 is a first light emitting part emitting light when themain switch 12 is turned ON. Since the main LED 15 emits light when themain switch 12 is turned on, the operator can easily confirm that themain switch 12 is ON/OFF.

The power supply circuit 16 converts the voltage output from the battery50 to a voltage of a value corresponding to the pulling rate of thetrigger 13 regardless of the output voltage magnitude from the battery50 and outputs it. The power supply circuit 16 further include afunction of protecting the battery 50 and drive part 30 againstovercurrent and overvoltage, imposing mandatory OFF on the outputaccording to the output voltage of the battery 50 or the value ofcurrent supplied to the drive part 30. Details of operation and aspecific circuit of the power supply circuit 16 will be described later.

Since the power supply circuit 16 applies to the drive part 30 a voltageof a value according to the pulling rate of the trigger 13 regardless ofthe output voltage of the battery 50, the type of the battery 50 doesnot matter. This embodiment is explained as a case in which the battery50 is, for example, a lithium ion rechargeable battery. The battery 50comprises a substrate, multiple battery cells provided on the substrate,and plus and minus terminals provided on the substrate. The battery 50also comprises an LD terminal. When a circuit provided on the substrateof the battery 50 detects overdischarge from the battery cells, abnormalsignals are output from the LD terminal. The battery 50 also comprisesan ID terminal. Battery information such as specification of the battery50 stored in the memory on the substrate of the battery 50 is outputfrom the ID terminal. The battery 50 applies a voltage between the plusand minus terminals to the power supply circuit 16.

As described later, the electric lawn mower 1 further comprises aspeaker, a radio, and a sound reproducing device, which are driven bythe electric power supplied from the operation part 10.

The coupling part 20 includes a hollow tube made of a lightweight, rigidmaterial such as aluminum alloy and reinforced plastic. The couplingpart 20 mechanically connects the operation part 10 and drive part 30and supplies the electric power output from the power supply circuit 16to the drive part 30 via a conductive wire running through the insidethereof.

Holding the D-shaped handle 21 and grip 22, the user uses the electriclawn mower 1. The operation part 10 and drive part 30 are provided onthe coupling part 20 at a distance as described above; therefore, thegravity center of the electric lawn mower 1 is away from the operationpart 10. The user receives a proper weight, improving the operability.

The drive part 30 rotates the attached blade 39 with the input electricpower. The drive part 30 consists of, for example, a coreless motor.

The drive part 30 consisting of a coreless motor assures a higher levelof quietness. Furthermore, a lithium ion battery is used to drive thecoreless motor; a lightweight, low power consumption electric lawn mower1 having extended operation time can be constructed. Furthermore, usinga booster circuit 300 as described later, sufficiently high rotationspeed operation is available with a small capacity battery.

The running indicator LED 40 is a second light emitting part emittinglight while the drive part 30 is powered. The running indicator LED 40consists of, for example, an organic EL. The running indicator LED 40emits light while the drive part 30 is powered. Then, the runningindicator LED 40 emits light even if the drive part 30 does not rotatebecause of, for example, shortage in torque. In this way, the user canknow whether or not the drive part 30 is powered from the runningindicator LED 40. Furthermore, when the user cannot know whether or notthe drive part 30 is driven from the driving sound of the drive part 30,the running indicator LED 40 allows the user to know whether or not thedrive part 30 is driven.

As shown in FIG. 2, the battery 50 is detachably fitted in the batterymounting part 11 in the direction from the top surface to bottomsurface. With the battery 50 being fitted in the battery mounting part11, the output terminals of the battery 50 are connected to the inputterminals of the operation part 10.

The drive part 30 consisting of a coreless motor primarily comprises, asshown in FIG. 3, a motor case 29, a coil substrate 31, a central shaft(output shaft) 32, a brush 33, a commutator 34, an upper yoke 35, alower yoke 36, a magnet part 37, and a brush cap 38.

The motor case 29 immobilizes the upper yoke 35, lower yoke 36, andbrush cap 38. The coil substrate 31 is secured by the central shaft 32passing through the center of the motor case 29. The commutator 34 isfixed to one surface of the coil substrate 31. The upper yoke 35 isfixed to the motor case 29 at a not-shown position. The lower yoke 36 isfitted in and fixed to the motor case 29. The magnet part 37 is fixed toone surface of the lower yoke 36. The brush cap 38 is fixed to the motorcase 29. The brush 33 is supported and biased toward the commutator 34by a spring that the motor case 29 includes.

The motor case 29 is a hollow case made of a lightweight, rigid materialsuch as aluminum alloy and reinforced plastic. The coil substrate 31 isa nearly disc-shaped plate on which multiple coils are arranged.

Passing through the coil substrate 31 and commutator 34, the centralshaft 32 is secured to the coil substrate 31. The coil substrate 31 andcommutator 34 rotates as one piece as the central shaft 32 rotates. Theelectric power supplied from the operation part 10 via a conductive wirepassing through the inside of the coupling part 20 is supplied to thecoil substrate 31 via the brush 33. The commutator 34 consists ofcommutator segments and insulating segments connected to the coilsubstrate 31 and alternately arranged in a circle around the centralshaft. The commutator 34 allows only one direction of current suppliedfrom the brush 33 to run to the coil substrate 31. The magnet part 37has planar magnets magnetized in the axial direction and arranged in thecircumferential direction, forming a magnetic circuit via the upper andlower yokes 35 and 36.

As shown in FIG. 4, the rotor of the coreless motor comprises a centralshaft 32, a flange 132, and, from the top in FIG. 4, a commutator 34 anda coil substrate 31 consisting of five coil substrate parts 131. Thecommutator 34 and coil substrate 31 are each a printed-wiring boardcomposed of an insulator substrate and a conductor pattern.

As shown in FIG. 5, a conductor pattern for commutator segments 134making contact with the brush 33 is formed on the top surface of thecommutator 34. The conductor pattern has an annular form around thecentral shaft 32 seen in the axial direction of the central shaft 32.Each commutator segment 134 has a through-hole penetrating thecommutator 34 at the outer end. A conductor pattern on the top surfaceof the coil substrate part 131 provides multiple coil segments 131 aarranged in a radial pattern about the central shaft 32 and bent ingiven directions about the axis of the central shaft 32.

As shown in FIG. 6, each coil segment 131 c is connected to thecorresponding commutator segment 134 via a through-hole at the innerend. Each coil segment 131 c has multiple through-holes penetrating thecoil substrate part 131 at the outer end.

A conductor pattern on the bottom surface of the coil substrate part 131is nearly equal to the coil segments 131 a and 131 c shown in FIGS. 5and 6 and provides multiple not-shown coil segments arranged in a radialpattern about the central shaft 32. The outer end of each not-shown coilsegment is connected to the corresponding coil segment on the topsurface via solder filled in the through-hole. The inner end of eachnot-shown coil segment is connected to the corresponding commutatorsegment 134 of the commutator 34 via solder filled in the through-hole.Then, the multiple coil segments 131 a and 131 c and multiple not-showncoil segments in the coil region constitute multiple coils in the formof a nearly horizontal U-shape (an example of a nearly annular form)seen in the axial direction of the central shaft 32. The multiple coilsare arranged in the circumferential direction around the central shaft32. The ends of the coils are connected to the corresponding commutatorsegments 134 of the commutator 34.

The conductor pattern for the commutator segments 134 of the commutator34 has a thickness larger than the coil segments of the coil substrateparts in order to curb damage due to abrasion by the brush 33. Not-showninsulating layers are interposed between the commutator 34 and coilsubstrate 31 and between multiple coil substrate parts 131.

The magnetic flux of the magnetic circuit formed via the upper and loweryokes 35 and 36 passes through the coils of the coil substrate 31 in theaxial direction of the central shaft 32. The motor case 29 housing themagnet part 37 and upper and lower yokes 35 and 36 constitutes thestator of the coreless motor. The central shaft 32 and coil substrate 31secured to the central shaft 32 as the rotor and the magnet part 37,upper and lower yokes 35 and 36, and brush 33 as the stator constitutethe direct current rectifier motor of the coreless motor. Here, themagnet part 37 and upper and lower yokes 35 and 36 constitute a magneticflux generation means forming a magnetic circuit. The magnetic fluxgeneration means is not restricted to this structure as long as themagnetic flux passes through the coils of the coil substrate 31 in theaxial direction of the central shaft 32. For example, the magnetic fluxgeneration means can consist of multiple permanent magnets,electromagnets, or only coils.

The blade 39 rotates in conjunction with the central shaft 32 rotates.As the blade 39 rotates, the target is mowed.

The connection between the operation part 10 and trigger 13 of theelectric lawn mower 1 in FIG. 1 is shown in detail in FIG. 7.

The grip 22 is formed integrally with the operation part 10 and providedalong the periphery of the coupling part 20. The grip 22 is providedwith a rotation shaft 25, to which the trigger 13 is coupled. A wire 24is connected to the trigger 13. The trigger 13 is coupled to a variablespeed switch 26 provided in the operation part 10 via the wire 24. Thegrip 22 may be close to the operation part 10 with a space therebetween,which is regarded as equivalent to a situation where the grip 22 is nextto the operation part 10.

When the trigger 13 is pulled, the wire 24 is tugged about the rotationshaft 25. The wire 24 transfers the pulling rate of the trigger 13 tothe variable speed switch 26. The variable speed switch 26 supplies thepulling rate of the trigger 13 to the power supply circuit 16. The powersupply circuit 16 adjusts the output voltage according to the pullingrate of the trigger 13.

The electric lawn mower 1 can have a U-shaped handle 23 as shown in FIG.8 in place of the D-shaped handle 21. In such a case, the U-shapedhandle 23 is provided on the coupling part 20 at a distance from theoperation part 10 and the trigger 13 is provided at one end of theU-shaped handle 23.

The U-shaped handle 23 consists of a U-shaped hollow pipe and has grips22 at the ends. The trigger 13 is provided to one of the grips 22.

As shown in FIG. 9, the U-shaped handle 23 comprises grips 22 at theends, a rotation shaft 25 at one of the grips 22, a trigger 13 coupledto the rotation shaft 25, a wire 24 coupling the variable speed switch26 in the operation part 10 to the trigger 13, and a resin cover 27covering the wire 24.

When the trigger 13 is pulled, the wire 24 is tugged about the rotationshaft 25. The wire 24 transfers the pulling rate of the trigger 13 tothe variable speed switch 26. The variable speed switch 26 supplies thepulling rate of the trigger 13 to the power supply circuit 16. The powersupply circuit 16 adjusts the output voltage according to the pullingrate of the trigger 13. The resin cover 27 protects the wire 24 frommechanical stress.

The power supply circuit 16 will be described hereafter with referenceto FIGS. 10 to 13.

The power supply circuit 16 comprises, as shown in FIG. 10, inputterminals I1, I2, I3, and I4, a main switch circuit 100, a triggerswitch circuit 200, a booster circuit 300, a speed adjustment circuit(speed adjustment part, voltage measuring part) 400, a control circuit500, a current detection circuit 600, a battery voltage detectioncircuit 700, a battery abnormality detection circuit 800, a constantvoltage circuit 900, and output terminals O1 and O2.

After the battery 50 is mounted on the battery mounting part 11, theinput terminal I1 is connected to the plus terminal (+) of the battery50; the input terminal I2, to the minus terminal (−) of the battery 50;the input terminal I3, to the LD terminal of the battery 50; and theinput terminal I4, to the ID terminal of the battery 50. On the otherhand, the running indicator LED 40 and drive part 30 areseries-connected between the output terminals O1 and O2.

The input terminal I1 is connected to the main switch circuit 100. Theinput terminal I2 is grounded. The input terminal I3 is connected to thebattery abnormality detection circuit 800. The input terminal I4 isconnected to the control circuit 500.

The output of the main switch circuit 100 is supplied to the triggerswitch circuit 200, battery voltage detection circuit 700, constantvoltage circuit 900, and anode of the main LED 15. The cathode of themain LED 15 is connected to the remaining battery level display 14. Themain switch circuit 100 consists of, for example, a switch activated asthe main switch 12 is turned ON and a self-arc extinguishing elementsuch as IGBT (insulated gate bipolar transistor) and MOSFET (metal oxidesemiconductor field effect transistor).

The trigger switch circuit 200 is connected between the main switchcircuit 100 and booster circuit 300. The trigger switch circuit 200consists of, for example, a switch activated as the trigger 13 is pulledand a self-arc extinguishing element such as IGBT and MOSFET. [0076] Thebooster circuit 300 is connected between the trigger switch circuit 200and output terminal O1. The booster circuit 300 is, for example, aflyback booster circuit. [0077]

The speed adjustment circuit 400 is so connected as to provide feedbackon the output of the booster circuit 300 to the booster circuit 300. Thespeed adjustment circuit 400 consists of, for example, a voltagedividing resistor and a variable resistor having a resistance variedaccording to the pulling rate of the trigger 13.

The control circuit 500 receives the output of the constant voltagecircuit 900, output of the current detection circuit 600, output of thebattery voltage detection circuit 700, and the input to the inputterminal I4. The output of the control circuit 500 is supplied to themain switch circuit 100, trigger switch circuit 200, and speaker 910.The control circuit 500 is, for example, a microcomputer.

The current detection circuit 600 is connected to the output terminal O2at one terminal and grounded at the other terminal. The currentdetection circuit 600 is, for example, an ampere meter.

The battery voltage detection circuit 700 is connected to the output ofthe main switch circuit 100 as described above. The output of thebattery voltage detection circuit 700 is supplied to the control circuit500.

The output of the battery abnormality detection circuit 800 is suppliedto the main switch circuit 100. The battery voltage detection circuit700 is, for example, an off-latch circuit.

The output of the constant voltage circuit 900 is supplied to thecontrol circuit 500, speaker 910, sound reproducing circuit 920, andradio 930. The constant voltage circuit 900 is a circuit outputting aconstant value voltage from the voltage output from the battery 50 andconsists of, for example, a three-terminal regulator and a smoothingcapacitor.

The power supply circuit 16 having the above-described structure isdriven by a voltage applied between the input terminals I1 and I2.

After the battery 50 is mounted on the battery mounting part 11,electric power is supplied from the battery 50 to the main switchcircuit 100.

The main switch circuit 100 is a switch associated with ON/OFF of themain switch 12. The main switch circuit 100 is turned ON when the mainswitch 12 is turned ON. The main switch circuit 100 is turned OFF whenthe main switch 12 is turned OFF. The main switch circuit 100 is furtherturned ON/OFF by the control circuit 500 while the main switch 12 is ON.

While the main switch 12 is ON, the main switch circuit 100 supplies theelectric power output from the battery 50 to the trigger switch circuit200, constant voltage circuit 900, and remaining battery level display14. While the main switch 12 is OFF, the main switch circuit 100 blocksthe electric power supplied from the battery 50.

The trigger witch circuit 200 is a switch associated with the trigger13. The trigger switch circuit 200 is turned ON when the pulling rate ofthe trigger 13 is equal to or higher than a given value. The triggerswitch circuit 200 is further turned ON/OFF by the control circuit 500.While the trigger switch circuit 200 is ON, the trigger switch circuit200 supplies the electric power supplied from the main switch circuit100 to the booster circuit 300. While the trigger switch circuit 200 isOFF, the trigger switch circuit 200 blocks the electric power.

The booster circuit 300 boosts the electric power supplied from thetrigger switch circuit 200 and outputs it from the output terminal O1.The output of the booster circuit 300 is adjusted by the speedadjustment circuit 400. The booster circuit 300 adjusts the output sothat the voltage input from the speed adjustment circuit 400 alwaysstays constant. The voltage boosted by the booster circuit 300 isapplied to the drive part 30 connected to the output terminals O1 andO2.

The speed adjustment circuit 400 is a circuit measuring the voltageapplied to the motor and adjusting the output of the booster circuit 300according to the pulling rate of the trigger 13. The speed adjustmentcircuit 400 provides feedback on the output of the booster circuit 300,whereby the booster circuit 30 outputs a voltage of a target value. Thespeed adjustment circuit 400 supplies the voltage divided between thevoltage dividing resistor and variable resistor to the booster circuit300.

The current detection circuit 600 detects the current running toward thedrive part 30 and outputs it to the control circuit 500. The batteryvoltage detection circuit 700 detects the voltage output from thebattery 50 and outputs it to the control circuit 500.

The control circuit 500 mandatorily turns OFF the main switch circuit100 or trigger switch circuit 200, for example, when the current runningtoward the drive part 30 exceeds the rated value of the drive part 30 orwhen the voltage output from the battery 50 becomes lower than a givenvalue. The control circuit 500 executes programs stored in the memory inadvance so as to turn OFF the main switch circuit 100 or trigger switchcircuit 200 according to the current running toward the drive part 30,which is detected by the current detection circuit 600, and the voltageoutput from the battery 50, which is detected by the battery voltagecircuit 700. Furthermore, when the control circuit 500 detects noelectric power being supplied to the drive part 30 for a given period oftime while the main switch circuit 100 is ON, the control circuit 500automatically turns OFF the main switch circuit 100. Furthermore, thecontrol circuit 500 receives battery information from the ID terminalvia the input terminal 4. Receiving battery information, the controlcircuit 500 makes reference to a table stored in the internal memory inadvance and reads the voltage at which the battery starts overlydischarging based on the battery information. For example, the controlcircuit 500 obtains an overdischarge voltage of 8 V if the batteryinformation includes a rated voltage of 14.4 V and an overdischargevoltage of 10 V if the battery information includes a rated voltage of18 V. The control circuit 500 automatically turns OFF the main switchcircuit 100 when the output voltage of the battery 50 becomes lower thanthe overdischarge voltage. The overdischarge voltage is a referencevoltage where the battery 50 reaches a state of overdischarge when theactual output voltage of the batter 50 constantly decreases. Also, theoverdischarge voltage is larger than this output voltage by apredetermined value. When the output voltage of the battery 50 fallsbelow the overdischarge voltage, the main switch circuit 100 isautomatically turned OFF as overdischarge occurs shortly thereafter.

The battery abnormality detection circuit 800 turns OFF the main switchcircuit 100 when it receives signals from the LD terminal andmandatorily keeps the main switch circuit 100 OFF until it receives noinput from the LD terminal or the battery 50 is dismounted.

The constant voltage circuit 900 is a circuit outputting a voltage of aconstant value from the voltage output from the battery 50. The outputof the constant voltage circuit 900 is supplied to the control circuit500 and also to the speaker 910, sound reproducing circuit 920, andradio 930.

The speaker 910 makes sound based on input sound information.

Furthermore, when the current detection circuit 600 detects more than agiven value of current running toward the drive part 30, the controlcircuit 500 instructs the speaker 910 to make sound for the case ofovercurrent. Similarly, when the battery 50 starts overly discharging,the speaker 910 announces the overdischarge. When the battery 50undergoes an abnormal event, the speaker 910 announces that the battery50 undergoes an abnormal event.

The sound reproducing circuit 920 operates on the output of the constantvoltage circuit 900. The sound reproducing circuit 920 decodes sounddata such as music data stored in the internal memory and outputs themto the speaker 910. The radio 930 has an antenna. The radio 930 tunesthe antenna properties and receives radio waves of a particularfrequency, detects sound information superimposed on carrier waves fromthe received radio waves, and outputs the detected sound information tothe speaker. These operations are performed on the output of theconstant voltage circuit 900; therefore, they are activated as the mainswitch circuit 100 is turned ON.

An example of a specific circuit of the booster circuit 300 will bedescribed hereafter.

As shown in FIG. 11, the booster circuit 300 consists of, for example, asmoothing circuit 301, a booster circuit 310, a rectifier diode 320, anda smoothing capacitor 330. The speed adjustment circuit 400 consists ofa series circuit composed of a voltage dividing resistor 410, a voltagedividing resistor 420, a variable resistor 430.

The smoothing capacitor 301 is parallel-connected between the triggerswitch circuit 200 and booster circuit 310. The booster circuit 310 isseries-connected between the trigger switch circuit 200 and rectifierdiode 320. The rectifier diode 320 is series-connected between thebooster circuit 310 and output terminal O1. The smoothing capacitor 330is parallel-connected between the rectifier diode 320 and outputterminal O1.

The speed adjustment circuit 400 is connected between the outputterminals O1 and 02. The output of the speed adjustment circuit 400 isconnected to the booster circuit 310. In the speed adjustment circuit400, the voltage dividing resistors 410 and 420 are series-connected andthe variable resistor 430 is further series-connected thereto.

The smoothing capacitor 301 removes extra vibration of the voltagesupplied from the trigger switch circuit 200 so as to smooth thewaveform.

The booster circuit 310 is a booster chopper circuit consisting of, forexample, an FET (field effect transistor) 311, a switching IC(integrated circuit) 312, and a choke coil 313.

With the switching IC 312 repeatedly turning ON/OFF the FET 311, thebooster circuit 310 boosts the input voltage by means of the flybackeffect of the choke coil 313 and outputs the boosted voltage.

The FET 311 is turned ON when a voltage equal to or higher than athreshold voltage is applied to the gate terminal by the switching IC312, allowing a current to run between the source and drain terminals.The FET 311 is turned OFF when a voltage lower than the thresholdvoltage is applied to the gate terminal, allowing no current to runbetween the source and drain terminals.

The switching IC 312 applies a high level of voltage equal to or higherthan a threshold voltage of the FET 311 or a low level of voltage lowerthan the threshold voltage to the gate terminal of the FET 311 to turnON/OFF the FET 311 according to the voltage input from the speedadjustment circuit 400. The switching IC 312 adjusts the ON/OFFswitching frequency of the voltage applied to the gate terminal of theFET 311 so that the voltage input from the speed adjustment circuit 400has a target value. For example, the switching IC 312 increases theON/OFF switching speed of the FET 311 when the voltage input from thespeed adjustment circuit 400 is lower than a target value, and decreasesthe ON/OFF switching speed of the FET 311 when the voltage input fromthe speed adjustment circuit 400 is higher than the target value.

The choke coil 313 yields flyback effect as the ON/OFF switching of theFET 311 occurs. The flyback effect causes the voltage between theterminals of the choke coil 313 to rise.

The rectifier diode 320 rectifies the output of the booster circuit 310.The smoothing capacitor 330 removes extra vibration of the voltagerectified by the rectifier diode 320 so as to smooth the waveform.

The voltage divided between the voltage dividing resistor 410 and thevoltage dividing resistor 420 and variable resistor 430 is supplied tothe switching IC 312.

The variable resistor 430 has a resistance varied according to thepulling rate of the trigger 13. The resistance of the variable resistor430 drops as the pulling rate of the trigger 13 is increased and risesas the pulling rate of the trigger 13 is decreased.

For example, as the user increases the pulling rate of the trigger 13,the resistance of the variable resistance 430 drops and the voltageapplied to the switching IC 312 from the speed adjustment circuit 400drops. Then, the switching IC 312 shortens the switching cycle of theFET 311. As the cycle of switching ON/OFF the FET 311 is shortened, thepeak value of the voltage between the terminals of the choke coil 313rises and the voltage supplied to the switching IC 312 from the speedadjustment circuit 400 rises.

As described above, the speed adjustment circuit 400 provides feedbackon the output of the booster circuit 300, whereby the booster circuit300 adjusts the output so that the voltage input from the speedadjustment circuit 400 always stays constant.

The above operation is performed also when the voltage supplied to thebooster circuit 300 from the trigger switch circuit 200 varies becauseof the decrease in the output of the battery 50, the replacement toanother battery from the battery 50, or the like. For example, when theoutput of the battery 50 drops, the voltage output from the boostercircuit 300 accordingly drops. As the output of the booster circuit 300drops, the voltage supplied to the booster circuit 300 from the speedadjustment circuit 400 drops. Then, the booster circuit 300 furtherraises the output voltage. The output voltage of the booster circuit 300is adjusted until the voltage input from the speed adjustment circuit400 has a target value.

In this way, the booster circuit 300 and speed adjustment circuit 400allow the electric lawn mower 1 to operate at a target rotation speedregardless of different output from the battery 50.

Incidentally, the voltage dividing resistors 410 and 420 and variableresistor 430 have relatively high impedances compared with the drivepart 30. Therefore, the speed adjustment circuit 400 consumes almost noelectric power.

The control circuit 500, current detection circuit 600, voltagedetection circuit 700, and battery abnormality detection circuit 800 ofthe power supply circuit 16 will be described hereafter with referenceto FIGS. 12 and 13.

As shown in FIG. 12, the current detection circuit 600 consists of, forexample, a current detection resistor 610, an operational amplifier 620,a grounding resistor 621, a feedback resistor 622, and a currentlimiting resistor 630.

The current detection resistor 610 connects the booster circuit 300,speed adjustment circuit 400, and drive part 30 and the ground. Theterminal of the current detection resistor 610 that is not grounded isconnected to the + terminal of the operational amplifier 620. The outputof the operational amplifier 620 is connected to its own − (minus)terminal via the feedback resistor 622 and further grounded via thegrounding resistor 621. Furthermore, the output of the operationalamplifier 620 is supplied to the control circuit 500 via the currentlimiting resistor 630.

The current detection resistor 610 detects the total current runningtoward the booster circuit 300, speed adjustment circuit 400, and drivepart 30. However, since the current running from the booster circuit 300and speed adjustment circuit 400 to the ground is much smaller inquantity than the current running toward the drive part 30, the totalcurrent running toward the booster circuit 300, speed adjustment circuit400, and drive part 30 is nearly equal in quantity to the currentrunning toward the drive part 30.

The operational amplifier 620, grounding resistor 621, and feedbackresistor 622 form a noninverting amplifying circuit. The + terminal ofthe operational terminal 620 serves as the noninverting input terminal(+) and the − terminal of the operational terminal 620 serves as thenoninverting input terminal (−). The noninverting input terminal (+) ofthe operational terminal 620 receives the voltage between the currentdetection resistor 610 and ground. The noninverting input terminal (−)of the operational terminal 620 is grounded via the grounding resistor621 and receives negative feedback on the output of the operationalterminal 620 from the feedback resistor 622. The amplified output islimited in current by the current limiting resistor 630 and supplied tothe control circuit 500.

Receiving a signal having a voltage equal to or higher than a thresholdfrom the current detection circuit 600, the control circuit 500mandatorily turns OFF the trigger switch circuit 200. Once the triggerswitch circuit 200 is mandatorily turned OFF, the electric powersupplied from the main switch circuit 100 is not supplied to the boostercircuit 300 even if the trigger 13 is pulled. Here, the currentdetection resistor 610, grounding resistor 621, feedback resistor 622,and current limiting resistor 630 are selected so that the controlcircuit 500 receives a signal having a voltage equal to or higher than athreshold when the detected current exceeds a nearly rated value of thedrive part 30 (for example, 15 A).

As described above, when the current running toward the drive part 30 isequal to or higher than a given value, the control circuit 500mandatorily turns OFF the trigger switch circuit 200. However, eventhough the trigger switch circuit 200 is turned OFF, the main switchcircuit 100 stays ON and the electric power is supplied to the constantvoltage circuit 900.

As described above, when the current detection circuit 600 detects thecurrent running toward the drive part 30 having an abnormal value, thecontrol circuit 500 mandatorily turns OFF the trigger switch circuit 200to stop the power supply to the drive part 30.

Furthermore, when the battery voltage detection circuit 700 detects theoutput voltage of the battery 50 being equal to or lower than a givenvalue, the control circuit 500 mandatorily turns OFF the main switchcircuit 100. The battery voltage detection circuit 700 consists of, forexample, as shown in FIG. 13, a series circuit composed of voltagedividing resistors 710 and 720.

The voltage dividing resistor 710 is connected to the output of the mainswitch circuit 100 at one end and to one end of the voltage dividingresistor 720 at the other end. The other end of the voltage dividingresistor 720 is grounded.

The control circuit 500 receives the voltage applied to the voltagedividing resistor 720. When the received voltage becomes equal to orlower than a voltage at which the battery 50 starts overly discharging,the control circuit 500 mandatorily turns OFF the main switch circuit100.

As described above, the battery voltage detection circuit 700 measuresthe voltage output from the main switch circuit 100 so as to measure thevoltage output from the battery 50 and supplies it to the controlcircuit 500. When the output voltage of the battery 50 that is detectedby the battery voltage detection circuit 700 has an abnormal value, thecontrol circuit 500 mandatorily turns OFF the main switch circuit 100 tostop the output of the battery 50. In this way, overdischarge of thebattery 50 is prevented.

Furthermore, when there is no voltage input from the current detectioncircuit 600 for more than a given period of time stored in the memorywhile there is voltage input from the battery voltage detection circuit700, the control circuit 500 mandatorily and automatically turns OFF themain switch circuit 100. In this way, the electric lawn mower 1 isautomatically powered off when it is left with the main switch circuitkept ON.

Furthermore, when the circuit provided on the substrate of the battery50 detects any abnormal event with the battery cells, the batteryabnormality detection circuit 800 automatically stops the power supplyfrom the battery 50.

As described above, the present embodiment drives the motor of anelectric lawn mower with fixed (stable) output regardless of the typeand output of the power source. Furthermore, the power source isautomatically turned off when the battery starts overly discharging, acurrent exceeding the rated value of the motor occurs, or the batteryundergoes some abnormal event.

The present invention is not confined to the above embodiment and hasvarious modifications and applications.

For example, in the above embodiment, the coupling part 20 is acylindrical pipe. The coupling part 20 is not restricted in shape to theabove-described embodiment as long as it has an electric wire inside forsupplying electric power from the operation part 10 to the drive part30. The coupling part 20 can be, for example, arc-shaped or made of ashape-changeable flexible material.

Furthermore, in the above embodiment, the remaining battery leveldisplay 14 is a liquid crystal screen. The remaining battery leveldisplay 14 is not necessarily a liquid crystal screen as long as theremaining battery level is known. For example, the voltage output fromthe battery 50 can be applied directly or via a voltage divider to alight emitting diode that widely changes brightness according to theapplied voltage. In such a case, the brightness of the light emittingdiode is proportional to the output of the battery 50. The brightness ofthe light emitting diode drops as the electric power of the battery 50diminishes and the voltage drops. Checking on the brightness of thelight emitting diode, the remaining level of the battery 50 can be knownby the user.

Furthermore, in the above embodiment, the running indicator LED 40indicates whether or not the drive part 30 is in operation. It is notnecessarily a light emitter. For example, sound from the speaker 910 canbe used to inform the operator. Alternatively, another speaker forannouncing the operation can be provided.

Furthermore, in the above embodiment, the control circuit 500 controlsthe ON/OFF of the main switch circuit 100 and trigger switch circuit 200upon overdischarge and overcurrent. It is not necessarily the controlcircuit 500 that is in charge of the control. For example, the followingstructure can be used when the current running toward the drive part 30exceeds a given value. A GTO (gate turnoff thyristor) isseries-connected between the battery 50 and drive part 30 and a Zenerdiode having a breakdown voltage nearly equal to the threshold voltageof this self-arc extinguishing element is connected to the gate of the

GTO so that a voltage exceeding the breakdown voltage is applied to theZener diode when a given value of current runs through the drive part30. In this way, the current runs into the gate of the GTO and the GTOis turned OFF when the current running toward the drive part 30 exceedsa given value. After the GTO is turned OFF, the electric power outputfrom the battery 50 is not supplied to the drive part 30.

Furthermore, in the above embodiment, the battery abnormality detectioncircuit 900 detects abnormal events of the battery 50 based on signalsfrom the LD terminal of the battery 50. It is not necessary based onsignals from the LD terminal. For example, the battery abnormalitydetection circuit 900 measures the temperature of the battery 50 anddetermines that the battery 50 is abnormal when the temperature exceedsa given temperature. Alternatively, the battery abnormality detectioncircuit 900 measures the resistance of the T terminal of the battery 50and detects any abnormal event of the battery according to theresistance of the T terminal. Furthermore, the battery 50 is a lithiumion battery in the above explanation. The battery can be a leadrechargeable battery or nickel-cadmium battery or even other kinds ofbatteries as long as it has capability of supplying electric power tothe power supply circuit 16. Here, when the battery 50 is a lithium ionbattery, which is lighter than a nickel-cadmium battery ornickel-hydrogen battery, a lightweight coreless motor can be used as themotor provided at the other end of the coupling part 20 with awell-balanced manner; an overall lightweight, well-operable electriclawn mower 1 can be provided.

Furthermore, in the above embodiment, the control circuit 500 makesreference to a table stored in the internal memory to determine thedischarging voltage of the battery 50 based on battery informationsupplied from the battery 50. This is not restrictive. For example, thedischarging voltage can be determined from specific informationcontained in battery information. In such a case, the dischargingvoltage can be half the rated voltage of the battery 50 that iscontained in battery information.

Furthermore, in the above embodiment, the operation part 10 and drivepart 30 are provided on the coupling part 20 at a distance from eachother. They are not necessarily provided at a distance or provided onthe coupling part 20 as long as the electric power output from theoperation part 10 is supplied to the drive part 30. For example, theoperation part 10 and drive part 30 can be provided at one end of thecoupling part 20 side by side or the operation part 10 and drive part 30can be connected only by a conductive wire without the coupling part 20.

The electric lawn mower 1 can have a blade 39 provided at an angle withrespect to the coupling part 20 as shown in FIG. 14. This allows theoperator to maintain his/her natural posture during general operation ofthe electric lawn mower 1 in which the operator swings his/her handsholding the grip (grip part) 22 (not shown) and D-shaped handle 21around his/her hip as indicated by the arrow O in FIG. 17. The electriclawn mower 1 shown in FIG. 14 is designed to have, for example, a totallength A of approximately 180 cm and a blade inclination angle B ofapproximately 38 degrees with respect to the coupling part, whereby theblade 39 is nearly parallel to the ground surface when the distance Cbetween the grip 22 and ground surface is 70 to 90 cm, which is slightlyabove the hip of the operator. Additionally, the D-shaped handle 21 canbe attached by the operator at any point on the coupling part 20. Thedistance E between the D-shaped handle 21 and grip 22, namely thedistance between the trigger 13 to which the operator applies a forceand the holding part of the D-shaped handle 21, is designed to be nearlyequal to the shoulder width of the operator, for example, at least 20 cmand desirably 30 cm, whereby the operator can perform the operation inhis/her natural posture.

A belt holder 28 holding a belt 65 that can be placed over a shoulder ofthe operator as shown in FIGS. 15 and 16 is provided between theD-shaped handle 21 and grip 22. As shown in FIGS. 15 and 17, the belt 65is engaged with the belt holder 28 and then the belt 65 is placed over ashoulder of the operator. The weight of the electric lawn mower 1 isreceived by the shoulder during the operation, less tiring the operator.

Furthermore, a 14.4 V or 18 V lithium ion (Li-ion) battery (lithiumrechargeable battery) or nickel-cadmium (Ni—Cd) battery having a commonmounting part can be mounted on the operation part 10 of the electriclawn mower 1. Incidentally, a 14.4 V lithium battery includes, forexample, eight lithium ion battery cells comprising, four battery cellsconnected in series while parallelly connected with other four,connected in series, of the eight battery cells and has a weight ofapproximately 550 g and a capacity of 3.0 Ah, or a 14.4 V lithiumbattery includes, for example, four series-connected lithium ion batterycells and has a weight of approximately 300 g and a capacity of 1.5 Ah.A 18 V lithium ion battery includes, for example, ten lithium ionbattery cells comprising, five battery cells connected in series, whileconnected to other five, of the ten battery cells connected in series,and has a weight of approximately 700 g and a capacity of 3.0 Ah, or a18 V lithium ion battery includes, for example, five series-connectedlithium ion battery cells and has a weight of approximately 400 g and acapacity of 1.5 Ah. A 14.4 V nickel-cadmium battery includes, forexample, 12 series-connected nickel-cadmium battery cells and has aweight of approximately 800 g and a capacity of 3.0 Ah. A 18 Vnickel-cadmium battery includes, for example, 15 series-connectednickel-cadmium battery cells and has a weight of approximately 1000 gand a capacity of 3.0 Ah.

The drive part 30 of the electric lawn mower 1 is relatively lightweightbecause of no gear or core. The motor case 29 is formed by moldingaluminum alloy. The summed weight of the drive part 30 and the blade 39is, for example, approximately 1500 g. Therefore, as shown in FIG. 14,the gravity center G1 of the electric lawn mower 1 when a 18 Vnickel-cadmium battery is mounted on the operation part 10, the gravitycenter G2 when a 18 V lithium ion battery having a capacity 3.0 Ah ismounted, the gravity center G3 when a 14.4 V lithium ion battery havinga capacity 3.0 Ah is mounted, and the gravity center G4 when a 14.4 Vlithium ion battery having a capacity of 1.5 Ah is mounted are all onthe drive part 30 side with respect to the D-shaped handle 21. In otherwords, the gravity center of the electric lawn mower 1 is always on thedrive part 30 side with respect to the D-shaped handle 21 with anybattery mentioned above being mounted on the operation part 10.

If the gravity center is located on the operation part 10 side withrespect to the D-shaped handle 21, the operator has to horizontallyswing the D-shaped handle 21 while lifting it. However, here, thegravity center of the electric lawn mower 1 is located on the drive part30 side with respect to the D-shaped handle 21, whereby the electriclawn mower 1 automatically lowers the coreless motor to the ground whilethe operator holds the electric lawn mower 1 by holding the grip 22 andD-shaped handle 21. The operator does not need to apply a force to lowerthe forefront of the electric lawn mower 1 during the operation, whichreduces the operator's workload and improves the operability. The beltholder 28 between the D-shaped handle 21 and grip 22 allows the corelessmotor to automatically fall to the ground when the belt 65 is placedover the shoulder, giving excellent operability. With the belt 65 beingplaced over the shoulder, the operator can hold the grip 22 in the rearof the belt holder 28 and applies to the grip 22 a force toward theground. In this way, the electric lawn mower 1 is supported by the beltholder 28 and grip 22. The electric lawn mower 1 can be swung about thebelt holder 28 simply by applying to the D-shaped handle 21 a force inthe swing direction. The blade 39 can easily be moved to the targetsite, improving the operability.

In the above embodiment, the motor case 29 is made of aluminum alloy.The motor case 29 can be made of resin and a weight can be provided nearthe drive part 30 to have the gravity center on the drive part 30 sidewith respect to the D-shaped handle 21. However, the motor case 29 madeof aluminum alloy provides better cooling action, which curbs rise inthe temperature of the coil substrate 31, and increases the strength,which improves the life.

Furthermore, the blade 39 of the electric lawn mower 1 is directlydriven by the central shaft 32 of the coreless motor, namely the blade39 is directly connected to the coreless motor without any gear or thelike, curbing mechanical loss. Furthermore, no gear noise occurs,curbing unwanted noise. Furthermore, the coreless motor rotates as amagnetic flux passing through the coil substrate 31 in the axialdirection of the central shaft 32 occurs. Therefore, the motor does notprotrude in the axial direction of the central shaft 32 even though themotor is provided where the drive part 30 side is (where the blade 39side is). The drive part 30 can significantly be downsized in the axialdirection of the central shaft 32. Therefore, any reduction in theoperability due to the protrusion of the drive part 30 in the axialdirection of the central shaft 32 is curbed.

The coreless motor in the above embodiment is a coreless motor having acoil substrate 31 in the rotor part and a brush 33 with a magnet part 37in the stator part. It can be a brushless-type coreless motor comprisinga coil substrate in the stator part and a magnet in the rotor part.

Furthermore, in the above embodiment, the gravity center is located onthe coreless motor side with respect to the D-shaped handle 21regardless of any battery, 14.4 V or 18 V lithium ion battery ornickel-cadmium rechargeable battery, being mounted. However, from theviewpoint of providing an electric lawn mower that is overalllightweight, well-balanced, quiet, and operable for a prolonged time,the structure allowing only lithium ion batteries to be mounted may beused.

Furthermore, in the above embodiment, an electric operating machineapplied to an electric lawn mower using an electric motor is described.The present invention is applicable to any electric machine andsimilarly applicable to a wide range of other operating machines usingan electric motor. Particularly, the present invention is suitable forsanders, polishers, routers, and dust collectors in which the rotationof an electric motor is directly transferred to the work tool (rotaryblade, fan, etc.) via no reduction gears.

Having described and illustrated the principles of this application byreference to one or more preferred embodiments, it should be apparentthat the preferred embodiments may be modified in arrangement and detailwithout departing from the principles disclosed herein and that it isintended that the application be construed as including all suchmodifications and variations insofar as they come within the spirit andscope of the subject matter disclosed herein.

This application claims the benefit of Japanese Patent ApplicationsJP2009-199066 filed Aug. 28, 2009, JP2009-229092 filed Sep. 30, 2009 andJP2010-006186 filed Jan. 14, 2010, the entire disclosure of which isincorporated by reference herein.

REFERENCE SIGNS LIST

-   1 electric lawn mower-   10 operation part-   11 battery mounting part-   12 main switch-   13 trigger-   14 remaining battery level display-   15 main LED-   16 power supply circuit-   20 coupling part-   21 D-shaped handle-   22 grip-   23 U-shaped handle-   24 wire-   25 rotation shaft-   26 variable speed switch-   27 resin cover-   30 drive part-   40 running indicator LED-   50 battery-   100 main switch circuit-   200 trigger switch circuit-   300 booster circuit-   400 speed adjustment circuit-   500 control circuit-   600 current detection circuit-   700 battery voltage detection circuit-   800 battery abnormality detection circuit-   900 constant voltage circuit-   910 speaker-   920 sound reproducing circuit-   930 radio

1. An electric operating machine comprising: a power source partincluding a battery mounting part for mounting a battery, and a voltageconversion part converting and outputting the voltage input from thebattery; and an electric motor to which a work tool rotating inassociation therewith is connected and that rotates upon application ofthe voltage output from the voltage conversion part, characterized inthat the power source part further includes a voltage measuring partmeasuring the voltage applied to the electric motor and outputting it tothe voltage conversion part; and the voltage conversion part adjusts theoutput voltage so that the voltage output from the voltage measuringpart has a given level.
 2. The electric operating machine according toclaim 1 characterized in that a battery of any voltage is mounted on ordismounted from the battery mounting part.
 3. The electric operatingmachine according to claim 1 characterized in that the power source partfurther comprises an overcurrent protection part blocking the currentrunning toward the electric motor when the current running toward theelectric motor exceeds a given value.
 4. The electric operating machineaccording to claim 1 characterized in that the electric operatingmachine further comprises a first announcing part announcing that anovercurrent is running when the current running toward the electricmotor exceeds a given value.
 5. The electric operating machine accordingto claim 1 characterized in that the power source part further comprisesan overdischarge protection part blocking the current running toward theelectric motor when the voltage output from the battery becomes lowerthan a predetermined voltage.
 6. The electric operating machineaccording to claim 1 characterized in that the electric operatingmachine further comprises a second announcing part announcing that thebattery is overly discharging when the voltage output from the batterybecomes lower than a predetermined voltage.
 7. The electric operatingmachine according to claim 5 characterized in that the power source partfurther comprises a voltage determination part determining thepredetermined voltage based on battery information of the battery thatis output from the battery.
 8. The electric operating machine accordingto claim 1 characterized in that the power source part further comprisesa battery abnormality stop part blocking the current running toward theelectric motor according to battery abnormality signals output from thebattery when the battery undergoes an abnormal event.
 9. The electricoperating machine according to claim 8 characterized in that the batteryabnormality stop part blocks the current running toward the electricmotor until the battery is dismounted from the battery mounting partsince it receives the battery abnormality signals.
 10. The electricoperating machine according to claim 1 characterized in that theelectric operating machine further comprises a third announcing partannouncing that the battery undergoes an abnormal event when the batteryundergoes an abnormal event.
 11. The electric operating machineaccording to claim 1 characterized in that the electric operatingmachine further comprises a trigger, and the voltage measuring partapplies to the voltage conversion part a voltage according to thepulling rate of the trigger.
 12. The electric operating machineaccording to claim 1 characterized in that the power source part furthercomprises a trigger switch part blocking the current running toward theelectric motor when the pulling rate of the trigger is lower than agiven rate and allowing a current to run through the electric motor whenthe pulling rate of the trigger is equal to or higher than the givenrate.
 13. The electric operating machine according to claim 12characterized in that the power source part further comprises a mainswitch part blocking the current running from the battery to the triggerswitch part when it is turned OFF and allowing the current when it isturned ON.
 14. The electric operating machine according to claim 13characterized in that the electric operating machine further comprises afirst light emitting part emitting light when the main switch part isON.
 15. The electric operating machine according to claim 1characterized in that the electric operating machine further comprises aremaining battery level display displaying the remaining battery levelaccording the voltage output from the battery.
 16. The electricoperating machine according to claim 1 characterized in that the powersource part further comprises a constant voltage circuit outputting aconstant voltage from the voltage output from the battery.
 17. Theelectric operating machine according to claim 16 characterized in thatthe electric operating machine further comprises a sound reproducingpart operating upon application of a voltage output from the constantvoltage circuit, decoding sound data, and reproducing sound information.18. The electric operating machine according to claim 16 characterizedin that the electric operating machine further comprises a radiooperating upon application of a voltage output from the constant voltagecircuit and detecting sound information in radio waves received by anantenna.
 19. The electric operating machine according to claim 16characterized in that the electric operating machine further comprises aspeaker amplifying the sound information and making sound by a voltageoutput from the constant voltage circuit.
 20. The electric operatingmachine according to claim 1 characterized in that the electric motor isa coreless motor.
 21. The electric operating machine according to claim20 characterized in that the electric operating machine furthercomprises a coupling part on whose one end the power source part isarranged and on whose other end the electric motor is arranged.
 22. Theelectric operating machine according to claim 1 characterized in thatthe electric operating machine further comprises a second light emittingpart emitting light when the electric motor is powered.
 23. The electricoperating machine according to claim 1 characterized in that theelectric operating machine further comprises a fourth announcing partannouncing the power supply when the electric motor is powered.
 24. Theelectric operating machine according to claim 20 characterized in thatthe coreless motor includes a rotor and a stator; the rotor includes afixed output shaft; one of the rotor and stator comprises a disc-shapedcoil substrate including multiple nearly annular coils arranged in thecircumferential direction around the output shaft when seen in the axialdirection of the output shaft; and the other of the rotor and statorcomprises a magnet generating a magnetic flux passing through the coilsubstrate in the axial direction of the output shaft.
 25. An electricoperating machine comprising: a coreless motor; a power source partcomprising a mounting part to which a lithium rechargeable battery isdetachably mounted; and a coupling part holding the coreless motor atone end and holding the power source part at the other end,characterized in that: the coreless motor includes a rotor and a stator;the rotor includes a fixed output shaft; one of the rotor and statorcomprises a disc-shaped coil substrate including multiple nearly annularcoils arranged in the circumferential direction around the output shaftwhen seen in the axial direction of the output shaft; and the other ofthe rotor and stator comprises a magnet generating a magnetic fluxpassing through the coil substrate in the axial direction of the outputshaft.
 26. An electric operating machine comprising: a coreless motor; apower source part comprising a mounting part to which a rechargeablebattery is detachably mounted; a coupling part holding the corelessmotor at one end and holding the power source part at the other end; agrip part extending in the longitudinal direction of the coupling part,including a trigger operable by the operator for controlling the driveof the coreless motor, and being continued from or close to the powersource part; and a handle provided on the coupling part at a distancefrom the power source part and grip part for being held by the operator,characterized in that: the coreless motor includes a rotor and a stator;the rotor includes a fixed output shaft; one of the rotor and statorcomprises a disc-shaped coil substrate including multiple nearly annularcoils arranged in the circumferential direction around the output shaftwhen seen in the axial direction of the output shaft; the other of therotor and stator comprises a magnet generating a magnetic flux passingthrough the coil substrate in the axial direction of the output shaft;and the coreless motor is heavier than the rechargeable battery mountedon the mounting part and the gravity center of the electric operatingmachine is located on the coreless motor side with respect to thehandle.
 27. The electric operating machine according to claim 26characterized in that the coreless motor comprises an aluminum alloymotor case housing the rotor.